/*
 ***************************************************************************************
 *  Copyright (C) 2006 EsperTech, Inc. All rights reserved.                            *
 *  http://www.espertech.com/esper                                                     *
 *  http://www.espertech.com                                                           *
 *  ---------------------------------------------------------------------------------- *
 *  The software in this package is published under the terms of the GPL license       *
 *  a copy of which has been included with this distribution in the license.txt file.  *
 ***************************************************************************************
 */
package com.espertech.esper.runtime.internal.kernel.statement;

import com.espertech.esper.common.client.util.SafeIterator;
import com.espertech.esper.common.internal.context.util.StatementAgentInstanceLock;

import java.util.Iterator;

/**
 * Implements the safe iterator. The class is passed a lock that is locked already, to release
 * when the close method closes the iterator.
 */
public class SafeIteratorImpl<E> implements SafeIterator<E> {
    private final StatementAgentInstanceLock iteratorLock;
    private final Iterator<E> underlying;
    private boolean lockTaken;

    /**
     * Ctor.
     *
     * @param iteratorLock for locking resources to safely-iterate over
     * @param underlying   is the underlying iterator to protect
     */
    public SafeIteratorImpl(StatementAgentInstanceLock iteratorLock, Iterator<E> underlying) {
        this.iteratorLock = iteratorLock;
        this.underlying = underlying;
        this.lockTaken = true;
    }

    public boolean hasNext() {
        return underlying.hasNext();
    }

    public E next() {
        return underlying.next();
    }

    public void close() {
        if (lockTaken) {
            iteratorLock.releaseReadLock();
            lockTaken = false;
        }
    }

    public void remove() {
        throw new UnsupportedOperationException("Remove operation not supported");
    }
}
